1. Field of the Invention
This invention pertains to apparatus and a method for measuring physical properties of particulate material. More particularly, the present invention pertains to apparatus and a method for measuring adhesion of particulate material.
2. Description of the Prior Art
In the art of rocket motor solid propellants, metallic powders are often included as fuel in various propellant formulations. One metallic powder which is often used is aluminum powder. Particles of commercially produced aluminum powders are covered with thin oxide layers. When such a powder is heated in the condition it is received from a commercial supplier, the particles tend to become sticky. The stickiness, or adhesion of particles to each other, influences the agglomeration and combustion behavior of the aluminum powder contained in a solid propellant. Accordingly, a method for controlling particle adhesion has been developed. The method comprises modifying and strengthening the aluminum oxide layers on the particles by means of heat treatment in an oxidative atmosphere.
Heretofore, there has not been a method of measuring particle adhesion in a way that is meaningful in solid rocket propellant research, although methods have been devised for measuring viscosity of molten plastics material, flow characteristics of granular materials, and viscosity of liquids. Commonly, viscosity measuring apparatus uses either a rotating probe immersed in the test liquid, or a calibrated aperture through which the test liquid drains.